Pittsburgh Steelers doctor James Bradley checks on the leg of Pittsburgh Steelers safety Troy Polamalu during the second quarter of Sunday’s game against the Philadelphia Eagles in Pittsburgh. The All-Pro aggravated his strained calf and has been ruled out the lineup this week.

PITTSBURGH — Troy Polamalu’s comeback turned out to be just a cameo, and there’s no telling when the Pittsburgh Steelers safety will be back on the field.

One thing’s for certain, it won’t be on Thursday when the Steelers (2-2) travel to reeling Tennessee (1-4).

Coach Mike Tomlin ruled Polamalu out of the lineup this week after the All-Pro aggravated his strained right calf in the first quarter of a 16-14 win over Philadelphia on Sunday.

Polamalu was in pass coverage when he pulled up at the end of the play and hobbled to the sideline. He spent the rest of the half sitting on the bench with his calf iced and watched the second half in sweats.

Tomlin pointed to the quick turnaround between games and the nature of Polamalu’s injury as the reasons behind the decision. Polamalu missed two games last month after originally straining the calf in a loss to Denver in the season opener.

The coach is a little more optimistic that linebacker LaMarr Woodley can play despite a strained right hamstring. Woodley sat out six games and missed parts of two others with a similar injury last year but Tomlin believes this time it isn’t quite as serious.

Still, with less than 100 hours to get ready, Woodley looks doubtful.

“Although there’s more optimism regarding where he is ... we’re at the early portion of the season and we’ve got to be smart with how we deal with that,” Tomlin said.

The news isn’t all bad, however, for Pittsburgh’s defense. Linebacker James Harrison didn’t miss a snap in his first game of the season and other than some minor swelling in his left knee on Monday, appeared just fine. He certainly looked just fine while recording two tackles and hurrying Philadelphia quarterback Michael Vick three times.

“I think that players of his caliber have inspired others,” Tomlin said. “You don’t deny that even if it’s somewhat intangible.”

There was nothing intangible, however, about the effect Harrison’s presence had on inside linebacker Lawrence Timmons. Freed up a bit by the attention the Eagles paid to Harrison, Timmons put together his finest performance of the season, recording a team-high nine tackles, a forced fumble and a pair of quarterback hits.

Timmons acknowledged the defense was playing with an “edge” it lacked at times earlier in the season.

“Everybody was running to the ball and having fun out there,” he said.

The Steelers need the fun to continue in Tennessee, though Pittsburgh has hardly been overwhelming on the road, dropping four of its last five dating back to last season.

The problem hasn’t been the offense, but the defense. The Steelers succumbed in the second half in road losses to Denver and Oakland, allowing the Broncos and Raiders to score on a seven of a possible eight possessions.

Big plays have been an issue too. The Broncos kickstarted a comeback in the opener thanks to a 71-yard touchdown pass from Peyton Manning to Demaryius Thomas and the Raiders dug themselves out of an early hole behind a 64-yard touchdown run from Darren McFadden.

“When you give up explosion plays, it decreases the chances of winning,” Tomlin said.

The Steelers have made a habit of playing to the competition away from Heinz Field. They struggled to beat woeful Cleveland, Kansas City and Indianapolis on the road last season and made the anemic Raiders look potent in a 34-31 loss two weeks ago.

The Titans are on pace for a historically bad season defensively, but the Steelers remain wary.

“We just need to respect the fact that we have yet to (win on the road) this year and we have an opportunity on Thursday night,” Tomlin said.

One that will come with another patchwork defense. The Steelers entered Sunday perfectly healthy for the first time this season. It lasted all of a quarter before Polamalu and Woodley were on the sideline.

Though Tomlin will give Ryan Mundy the first crack at filling in for Polamalu, he allowed there’s a chance veteran Will Allen could see an uptick in playing time. Mundy drew mixed results over the season’s first month and showed a penchant for making illegal hits.

He knocked out Oakland’s Darius Heyward-Bey with a helmet-to-helmet hit two weeks ago and was flagged 15 yards on Sunday for smacking into Philadelphia’s Jeremy Maclin after a short completion.

The Eagles eventually turned the flag into a touchdown that drew them within 10-7.

The flag was one of nine thrown against the Steelers on Sunday and Pittsburgh has already committed 37 penalties for 346 yards this season, uncharacteristically high number for a team that likes to consider itself one of the more disciplined in the league.